Variable output transformer system



March 8, 1949. J. c. MCDONALD 2,463,546

VARIABLE OUTPUT TRANSFORMER SYSTEM Filed Sept. 13. 1944 2 Sheets-Sheet 1 SFCT/ON 1' IN! [N TOR. c 906W 8. QIZmDO MQ Eli-.1

March 8, 1949. J. c. M DONALD 2,463,545

I VARIABLE OUTPUT TRANSFORMER SYSTEM 2 Sheets-Sheet 2 Filed Sept. 13. 1944 m n in Patented Mar. 8, 1949 UNITED STATES PATENT OFFICE VARIABLE OUTPUT TRANSFORMER SYSTEM John C. McDonald, New York, N. Y.

Application September 13, 1944, Serial No. 553,906

6 Claims.

My invention relates broadly to railway trafflc control systems and more particularly to a safety system of railway signaling which insures progressive operation of track signals over an extended series of coextensive blocks.

One of the objects of my invention is to provide a track circuit power supply system for automatically maintaining the current and/or voltage in the coextensive blocks of a trackway at a predetermined normal value regardless of the tendency of the track circuit to vary in impedance with changes in condition of weather for insuring continuous reliable and efiicient operation of the signaling system throughout the multiplicity of coacting blocks.

Other and further objects of my invention reside in the novel arrangement of relay circuits and current and voltage controlling circuits in a railway signaling system as will be set forth more fully in the specification hereinafter following by reference to the accompanying drawings in which:

Figure 1 is a diagrammatic circuit arrangement of one of the sections of the trackway circuit in a system ofrny invention showing the position of the control relays and the associated power supply and control circuits; Fig. 2 is a diagrammatic view showing the power control circuit of my invention by which current in each section of a railway trackway circuit is maintained at a predetermined level regardless of changes in trackway inpedance incidental to the wide fluctuation in moisture content of the trackway under conditions of change from an extremely dry to severely wet condition; and Fig. 3 is a diagrammatic view showing a modification of the power control circuit that may be applied to track sections adjacent a track crossing for also indicating train approach in a preceding section in addition to regulating the current level to the track section under conditions of varying track circuit impedance such as may be brought about by variable weather conditions.

The system of my invention provides for efl'icient and reliable operation of railway trains at high speeds. The development of railways for high speed operation has progressed so rapidly that safety measures for prevention of accidents incidental to high speeds have become essential. Many bridge accidents have involved collisions that could have been prevented by utilization of the progressive block signal system of my invention. My system provides for the supplying of power at substantially constant level to the sections of a block system of a trackway irrespective of the change in conductivity of the road-bed with changes in condition of the weather. I provide a system of relays which coact through circuits that I term M, A and N circuits extending from block to block for progressively actuating signals to indicate the occupied or unoccupied condition of the traclrway for a multiple number of sections ahead of the train.

Undoubtedly the most difficult problem in track signaling is to insure enough current through the rails to operate the track relay in bad weather. This is simply because, under those conditions, the ballast leakage between rails approaches the value of a metallic shunt across them and may equal that value if the section is long enough. Hence all systems are limited for this reason, in the length of section possible. All characteristics of the circuit employed affect the section length achieved for safe operation. However, with the use of M, A and N circuits hereinafter described, this leakage problem is reduced to that of one section. Usually the leakage existing in one section is not prohibitive and therefore, train control over 12,000 to 25,000 feet may be accomplished without ballast leakage being the controlling factor. For sections of normal length the regulation system of my invention functions with great reliability.

Many advantages result from the use of M, A and N circuits, among which are:

1. The reduction of ballast leakage effect on train control to one section length. No two sections are connected to one track relay but connection of control from one section to the next is through the M, A and N circuits. The net result, therefore, is that control is exercised over five sections behind the train with ballast leakage of one section only in any one circuit, with a consequent improvement ratio in the worst of all track signaling complications of five to one.

2. The flexibility of the number of sections over which train control may be exercised; one to four or five or more.

3. The use of existing sections and the present signaling equipment for achieving train control suitable for high speed operation, entailing a minimum of change 4. The securing of train control without a train in the section ahead, but rather, two to six sections ahead.

The components of the track circuit system will be described in detail hereinafter:

Track relay 7.A split-phase track relay having five single pole double throw contacts 1, 2, 3,

Estimated Minimum current required in relay coil to operate roley milli-amperes Number of points Contactors 8.--Two double-pole single-throw A.-C. contactors, 30 amperes contact-carrying capacity, used to complete the power supply circuit to the rails I5 with whatever current may be required for either lon -or short sections, which current might be greater than the normal capacity of the contact points of the track relay 1. The use of contactors 8 provides for suflicient current carrying capacity to permit sections up to 15,000 feet to be readily utilized. The currentcarrying capacity of the contacts l5 of the track relay 1 is normally about four amperes.

The contactor operating coils l6 and H are supplied from the local power source through transformer l8 and the circuit for either contactor is closed or opened by the first two contacts I and 2 on relay 1, These contactors may be provided with auxiliary interlock circuits to assure only one set of contacts being closed at any one time.

Track transformer banks 18.-A transformer I8 is located in each section with its primary winding connected to the power line l9 contiguous to the trackway and its secondary arranged to supply local power to the relay circuits of each section as shown.

"Miniature track transformer bank 20.-A pair of transformers 2i and 22 have their primary windings Ma and 22a disposed in series and connected to the winding of relay X while their secondaries 2") and 22b are connected in parallel. Primary winding 2 la connects with the power supply transformer Ill. The capacity of transformer bank 20 is sufficient to operate the coil of relay X. Voltage, output, etc. of miniature transformer bank 20 depends on the design of relay X.

Relay 9.A voltage relay, normally energized by circuit -N which is fed from the local power supply transformer in the section ahead, through a front contact of relay 10 in the section ahead. Green lamp circuit G is broken through a front point of this relay 9 when this relay is deenergized.

Relay 10.-A voltage relay, normally energized by circuit A which is fed from the local supply transformer in the section ahead, through a front point of relay H in the section ahead. Green lamp circuit G is broken the same as stated for relay 9.

Relay 11.A voltage relay, normally energized by circuit M which is fed from the local supply transformer in the section ahead through a front contact of relay X in the section ahead. Green 4 lamp circuit G is broken the same as stated for relay 9.

Bus BXC.--Connected to one back contact of each of relays 9, i0 and H; and to a front contact of relay 1 leading to the yellow lamp Y and to the operating coil of relay XAA; and to one back contact of relay X leading to a front contact of relay 1 thence to the left swing point 23 of relay 1, and to wire a of local supply circuit. Bus BXC therefore makes five connecting points. Bus BXC is energized when any one of relays 9, "I, II and X are de-energized.

Relay X.A voltage relay, normally energized. In this position, it holds circuit M energized to the section behind. When the track relay 1 of adjacent section II (for example) has its swing point 23 to the left, a shunt is placed across the operating coil of relay X in the adjacent section II which is thus de-energized.

In a trackway system having a multiplicity of coacting track sections identified for example as sections I, II, III, IV and V, includin components as set forth hereinbefore the sequence of operation would be as follows: A shunt across the operating coil of relay X:

Opens circuit M of section III Relay ll of section III is de-energized and opens circuit A of section IV Relay I0 of section IV is de-energlzed and opens circuit N of section V De-energizes relay 9 of section V Causes the following signal indications to show, as a result of the actions in sections I, II, III, IV and V:

Signal Indication red for section 11. yellow [or section III. yellow for section IV. ycllowfor section V. V-.. yellow for section VI. II, III, IV and V Bus BXO energized.

miniature track bank 20 which keeps relay X normally energized. Failure of relay X winding will produce a yellow indication in the section behind the location of the failed relay.

Relay XA.-A voltage relay whose sole pu pose, when used with circuits M, A and N, is to connect and impose 141 cycles or high speed frequency from supply line 21 on the rails of the section behind. Under these conditions, the section ahead, namely section V, is clear and relays 9, I0 and II are energized. This keeps relay XAA de-energized. This fact also causes the swing point 23 of relay 1 of section VI to be at the right. The energy to the coil of relay XA is completed from the local supply to a front contact of relay 7, right swing point 23 of relay 1, and top back point of relay XAA. Contacts of relay XA are closed, thus connecting 141 cycles of high speed control frequency from circuit 21 to rails ii of section VII, and this means that all trains in section VII and farther back may travel at high speed.

Relay XAA.--A voltage relay with three single pole, double throw contacts. Its purposes are:

(a) To carry the circuit for relay XA as described above, when de-energized (b) To connect and impose 94 cycle or restricted speed frequency on the rails l5 when energized.

The operating coil of relay XAA receives its energy supply from the local supply transformer l8 through bus EKG, and a front point of relay 1.

Booster transformer system 31.This device comprises a power transformer 32 with primary winding 33 connected to power source l3 and secondary winding 34 connected at one end with the contactors 8 and at the other end to the multiple transformer arrangement 35 and 35 as shown, Transformer 35 has the primary winding 35a thereof connected in parallel with primary winding 36a of transformer 36 and the conjoint arrangement of primary windings 35a and 36a disposed in series with contactors 8. Thus a series impedance is included in the power circuit feed path to the rail system l5 which is so arranged that it is capable of change in value in proportion to changes in trackway impedance due to changes in weather conditions. The secondary windings 35b and 3611 are connected in parallel and operate cumulatively. Adjustable resistance 31 is connected permanently across the secondary 35b while adjustable resistance 38 is connected intermittently to the secondary circuit through relay contacts W only when a predetermined ballast value is reached. Relay contacts W are controlled by winding 39 connected in series with the primary windings 40a of booster transformer 40 across the power supply leads H which extend to the contactors 8 and track circuit 15. The secondary winding 40b of transformer 40 connects in parallel with the secondary winding 34 of the power supply transformer 32. The primary and secondary Windings of the transformers are so arranged as to increase the voltage in the circuit to which the booster is connected when the load in that circuit is increased: Thus the voltage tends to remain constant and does so within reasonable limits, subject to the regulation of the system behind the booster (toward power source) and that of the booster itself. The voltage supplied to the rail circuit depends entirely upon the requirements of that circuit due to weather conditions.

The current control system of my invention is set forth more fully in the circuit arrangement of Fig, 2. In this arrangement I interpose a current transformer 42 in the series circuit that includes the secondary windings b and b of the two transformers 35 and 40. The current transformer 42 has its primary winding 42a directly in the series path operating cumulatively through transformers 35 and 4D. The current transformer 42 has secondary winding 4217 which connects to the relay winding 43. Relay winding 43 controls an armature and a front contact arranged in a manner similar to the arrangement illustrated in Fig. l for effectively cutting in the variable resistance 38 across the secondary circuit through relay contacts H. I term the relay circuit of Fig. 2 the H circuit as distinguished from the W circuit of Fig. 1. As current demands in rail circuit l5 increase due to bad weather conditions, current in secondary winding 42b increases thus increasing the current in the winding of relay H. At a predetermined point or value of current the contact system of relay H closes and increases the resistance unbalance of transformers 35 and 40. The current available for the rails I5 is thus increased. For purposes of adjusting the characteristics of the series circuit I provide a series impedance 44 in the series circuit which includes the secondary windings 35b and 40b and the primarywinding 42a. The impedance may be a variable inductance having a variable tap 44a thereon which is movable to selected positions along inductance for exactly controlling the current condition which will operate H relay 43. Thus each section will be assured of a proper value of current for operating the track relay 1 independently of the number of sections which are interrelated such as sections I-IV.

In Fig. 3 I have shown a further application of the H relay circuit for providing approach lighting in selected sections which have grade crossings therein. A supplemental relay is provided in the series secondary circuit which I have indicated as the Y relay. The Y relay includes a winding 45 which is energized through a transformer system 46 independently of the transformer 42 Transformer 46 has a primary winding 46a in series with the secondary series circuit. Primarywinding 46a is coupled to secondary winding 461) which connects to the operating winding 45 of the Y relay. The Y relay includes an armature and front contact system in series with the approach lighting load 41 energized from the power supply source 19.

The adjustable reactance coil 44 of Fig. 2 is put there only to keep the secondary load balanced, so that the load will be coming from each transformer 35 and 40 in equal measure. Now, because the reactance produces a loss, I can utilize that loss by substituting for the reactor 9. current relay circuit as shown in Fig. 3 at 46-45, and still maintain the load on both transformers 35 and 40 balanced, all at no extra expense.

This current relay 45 will pick up the approach lighting only with a train shunt on rails 15 and not by the ballast leakage. Part of the secondary load 38 is controlled to come on when the ballast leakage reaches a definite value, which automatically raises the secondary current in the transformer windings 35b and 36b. The maximum ballast leakage shunt value on rails should be approximately .133 ohm for a 15,000 foot section, while the train shunt is .02 ohm. That is, with maximum ballast leakage, the total shunt across rails would be the joint resistance of .02 and .1333-a very good short. This dead short can pull from the transformer only its normal safe loadand not a short circuit load.

The capacity of each transformer 2| and 22 in the miniature train bank 20 is approximately 30 watts. The normal Clear section power used is about 10 watts. With train in section ahead, the power consumption is zero, because the only thing that happens is that both transformers are now in parallel and balanced, and no load is pulled off at all as long as train stays in the section ahead.

With. section ahead Clear, the miniature track banks 20 are a little out of balance and current then flows in the secondary loop, which is what energizes relay X. When transformers 2l--22 are balanced, as is the case with the train in section ahead, no circulating current flows in the secondary .loop of the miniature track bank 20 at all. The only time when the maximum current fiows in the secondary loop is in the event that the relay winding of relay X should open, or the wiring to relay X should open. If that happe is, a maximum load of about 30 watts is drawn. A five ampere fuse is in one feed leg to the miniature track bank 20 indicated at 49 is provided, which fuse will automatically open and keep the feed off the system until the fault is corrected. Indicating fuses are used at the position 453 to facilitate instant discovery of the power condition in miniature track bank 20.

The a wire feeding the miniature track bank 20 must be kept tied to the a wire of the local signal lamp supply, in the event they happen to be of different voltages, as the a wire is connected to the swing point 23 of track relay 1, which ties to the .1) Wire of the miniature track circuit 20. If the wires are from same voltages and off the same supply, no such tie-in is necessary, of course.

This Y relay will close and pick up the approach lighting circuit only when train is in section. The H relay will also pick up, due to presence of this same train in section. But the ballast leakage, when it is picking up the H relay, does not pick up the Y relay at all. It takes a train in the section to do that.

The H relay and the Y relay are designed to pick up at different current values of the secondary loop. The H relay picks up at a lower value than the Y relay. When the current in the secondary loop rises enough to pick up the Y relay, by train in section, H relay must also pick up, as it is cut in on the same circuit, and responds to pickup at a much lower current value of the secondary loop.

In a case where only the H relay is connected in a section, as in Fig. 2, and approach lighting is not provided in that section, the H relay will always pick up with train in section, no matter what the ballast leakage value is at that time, but will drop open again as soon as the train clears the section, provided the ballast leakage is not too high.

Throughout the description of the system of my invention I contemplate the use of circuit elements of adequate size and construction to carry the current conditions which may occur over a wide range of variable conditions. I have illustrated the general arrangement of circuit elements required in the coaction of the several parts of the circuit system, but I desire that it be understood that modifications of my invention are intended and that my invention as set forth herein should be considered in the illustrative sense and not in a restricted sense. No' limitations upon my invention are intended other than may be imposed by the scope of the appended claims.

What I claim and desire to secure by Letters Patent of the United States is as follows:

1. In a system of the class described, a load circuit, a power supply system for said load circuit, a relay connected with said load circuit, means interposed between said power supply system and said load circuit for controlling the energization of said load circuit in proportion to the impedance thereof, comprising a pair of transformers including primary and secondary windings with the primary windings thereof connected in parallel and disposed in series with the power supply system and said load circuit, the secondary windings of said transformers being connected in parallel so that the instaning primary and secondary windings with the primary winding thereof connected in series with said relay control winding across said load circuit and the secondary Winding thereof connected across said power supply system, whereby an increase in current in said load circuit has the effect of energizing said relay control winding for operating said contactor and introducing said additional impedance in circuit with said first mentioned pair of secondary windings for increasing the current supply to the load circuit from said power supply system.

2. In a system of the class described, a load circuit, a relay controlled by said load circuit, a power supply system for supplying power to said load circuit, means interposed between said power supply system and said load circuit for increasing the current supply to the load circuit as the load increases, said means including a normally balanced transformer circuit electrically balanced to normall supply predetermined operating current to said load circuit for operation of said relay and means for unbalancing the electrically balanced condition of said balanced transformer circuit upon increase in load of said load circuit for supplying a compensating current from said power supply system to said load circuit.

3. In a system of the class described, a load circuit, a relay controlled by said load circuit, a power supply system for supplying power to said load circuit and means interposed between said power supply system and said load circuit for controlling the current supply to said load circuit, said means comprising a normally balanced transformer circuit, said balance-d transformer circuit including a pair of transformers each having primary and secondary windings with the primary windings thereof connected in said power supply system and the secondar windings thereof cumulativel coupled for drawing a predetermined current supply to said load circuit, an auxiliary transformer associated with said balanced transformer and means connected with said auxiliary transformer for controlling the impedance of the cumulatively coupled secondary circuit of said balanced transformer for increasing the current supplied to the load circuit in proportion to the increase in load thereof.

4. In a system of the class described, a load circuit, a relay controlled by said load circuit, a power supply system for supplying power to said load circuit, means interposed between said power supply system and said load circuit for controlling,

the current supply to said load circuit comprising a, balanced transformer circuit including a pair of transformers, each having primary and secondary windings with the primary windings thereof connected in parallel and disposed in a series circuit between said power supply system and said load circuit and the secondary windings thereof cumulativel coupled to a balancing circuit, an impedance normally connected in said balancing circuit, a separate impedance connect able with said balancing circuit and means connected with said balancing circuit and operative upon increase in current therein for including said connectable impedance in said balancing cirsaid load circuit and cult for increasing the current supplied to the circuit in proportion to the increase of load thereof.

5. In a system the class described, a load circuit, a relay controlled by said load circuit, a power supply system for supplying power to said load circuit, means interposed between said power supply system and said load circuit for controlling the current supply to said load circuit, comprising a balanced transformer circuit including a pair of transformers, each having primary and secondary windings with the primary windings thereof connected in parallel and disposed in a series circuit between said power supply system and said load circuit and the secondary windings thereof cumulatively coupled to a balancing circuit, a resistance normally connected in said balancing circuit; a separate resistance connectable with said balancing circuit, and means connected with said balancing circuit and operative upon increase in current therein for including said connectable resistance in said balancing circuit for increasing the current supplied to the'load circuit in proportion to the increase of load thereof.

6. In a system of the class described, a load circuit, a relay controlled by said load circuit, a power supply system for supplying power to said load circuit, means interposed between said power supply system and said load circuit for controlling the current supplied to said load circuit, comprising a balanced transformer circuit including a pair of branch circuits, means in said branch circuits operative at diflering current amplitudes,

, 1Q an impedance, circuit controlled by one of said means and connectable with said balanced transformer circuit, means connected with the other of said means and operative at a differing current value in said balanced circuit whereby current is supplied from said power supply system to said' load circuit for normal operation ofsaid load relay with a normal balanced condition of said balanced transformer circuit and wherein said first mentioned means operates to effect an increase in current to the load circuit as the load increases.

JOHN C. McDONALD.

REFERENCES crrnn The following references are of record in the ille of this patent:

UNITED STATES PATENTS 

